This invention relates to methods and apparatus for use in connection with the preparation of coke from crude petroleum products.
A "delay coker" is an apparatus for the preparation of coke from the heaviest portion of crude oil (commonly referred to as "bunker" fuel). The crude is generally heated to a temperature of about 800-900.degree. C. and then fed into the bottom of a coke drum. The coke drum has a diameter on the order of 25 feet and may be 80-90 feet high. At an elevated pressure (e.g., 30 pounds or more), the heated crude is thermally decomposed to leave a coke residue. During the thermal decomposition, lighter products such as hydrocarbons gases, gasoline and jet fuel, are recovered from the top of the coke drum. The decomposition process takes on the order of 16-20 hours to complete.
The solid residue is treated with steam to remove any entrained volatile hydrocarbons. The residue is then cooled down with water. Finally, the coke drum is opened at both the top and the bottom, and the solid product is drilled out for recovery. A typical drilling procedure employs a rotating high pressure water drill (for example, using 3000 lb/in.sup.2 pressure).
It has heretofore been necessary after lowering the stem of the drilling device into the drum to manually mount the drill in position, for example using some type of collar means. In one arrangement, a two-piece hinged collar having a generally circular shape was used to align and mount the drill stem. The collar was hoisted onto the drum in an open position, after which the two generally semicircular halves of the collar connected at one end were manually engaged around the drill by swinging them together. The collar was finally clamped to a flange on the top of the coke drum to fix the drill stem into position. The two halves of the collar were suitably joined together at one end by pins, so that the arms could be swung away from the position of engagement when not in use.
A principal disadvantage of the known arrangements for aligning and mounting the drill stem is the need for manual adjustment of the collar. Because of the heat generated in the coke drum, the top flange of the coke drum and the collar itself could be quite hot. Moreover, during the engagement and clamping operations, workers could be exposed to steam and residual heated hydrocarbons escaping from the steam-treated solid materials in the drum. In addition, movement of the drill stem could cause the collar to slide out of engagement position or off the top flange of the coke drum if it were not already clamped securely in place.
Accordingly, it is an object of the present invention to provide apparatus and methods for bringing the drill stem into engagement and proper alignment with the top end of a coke drum, which apparatus and methods would eliminate the need for direct operator contact with the coke drum and/or associated elements.